Vapor compression refrigerating systems

ABSTRACT

A vapor compression refrigerating system includes a compressor, a radiator connected to the compressor via a first tube, a first pressure reducing mechanism connected to the radiator via a second tube, and a separator connected to the first pressure reducing mechanism via a third tube and the compressor via a fourth tube. The separator includes an oil separator which is configured to separate an oil from the refrigerant, and a liquid and gas separator formed integral with the oil separator. The liquid and gas separator is configured to separate a liquid portion and a gas portion from the refrigerant, and the separator is further configured to transmit the oil and the gas portion to the compressor via the fourth tube. The system also includes a second pressure reducing mechanism connected to the separator via a fifth tube, and an evaporator connected to the second pressure reducing mechanism via a sixth tube and operationally coupled to the compressor via a seventh tube. The second pressure reducing mechanism is configured to receive the liquid portion from the separator.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to vapor compressionrefrigerating systems. In particular, the present invention relates tovapor compression refrigerating systems in which a separator includes anoil separator integrated with a gas and liquid separator to form asingle separator, and a gas portion of a refrigerant and an oilseparated from the refrigerant flows from the separator to a compressorvia the same tube, such that the size and the weight of the vaporcompression refrigerating systems is reduced.

2. Description of Related Art

Freon group refrigerants have been used in known air conditioningsystems, Nevertheless, the use such Freon group refrigerants has begunto be restricted due to environmental concerns. In Europe, it has beenproposed that carbon dioxide be used as a refrigerant in place of Freon.Carbon dioxide refrigerant is poison less and incombustible, however,the theoretical energy efficiency of carbon dioxide as a refrigerant isrelatively low, there are problems associated with improving theefficiency of carbon dioxide as a refrigerant. Moreover, when carbondioxide is used as a refrigerant, because a high-pressure side may reacha super critical condition which exceeds a critical pressure, it isnecessary to use materials that may bear this pressure. Consequently,the thickness of the materials increases, which increases the weight ofthe air conditioner system.

One known method of improving the efficiency of carbon dioxide as arefrigerant, which is described in Japanese Patent Publication No.JP-A-2000-274890, is to use an oil separator to prevent the circulationof oil to components other than the compressor. Nevertheless, the oilseparator increases the size of the air conditioner. Moreover, if oilflows into the evaporator, its heat transfer coefficient and itscoefficient of heat exchange are reduced.

SUMMARY OF THE INVENTION

Therefore, a need has arisen for vapor compression refrigerating systemswhich overcome these and other shortcomings of the related art. Atechnical advantage of the present invention is that a separator maycomprise an oil separator integrated with a gas and liquid separator toform a single separator, and a gas portion of the refrigerant and an oilseparated from the refrigerant may flow from the separator to acompressor via the same tube, such that the size and the weight of thevapor compression refrigerating system may be reduced relative to theknown vapor compression refrigerating systems.

According to an embodiment of the present invention, a vapor compressionrefrigerating system comprises a compressor configured to compress arefrigerant, and a radiator connected to the compressor via a firsttube. The radiator is configured to receive the refrigerant from thecompressor and to radiate the refrigerant. The system also comprises afirst pressure reducing mechanism connected to the radiator via a secondtube, and the first pressure reducing mechanism is configured to receivethe refrigerant from the radiator and to reduce a pressure of therefrigerant. Moreover, the system comprises a separator connected to thefirst pressure reducing mechanism via a third tube and the compressorvia a fourth tube, and the separator is configured to receive therefrigerant from the first pressure reducing mechanism. The separatorcomprises an oil separator which is configured to separate an oil fromthe refrigerant, and a liquid and gas separator formed integral with theoil separator. The liquid and gas separator is configured to separate aliquid portion and a gas portion from the refrigerant, and the separatoris further configured to transmit the oil and the gas portion to thecompressor via the fourth tube. The system also comprises a secondpressure reducing mechanism connected to the separator via a fifth tube,and the second pressure reducing mechanism is configured to receive theliquid portion from the separator and to reduce a pressure of the liquidportion. Moreover, the system comprises an evaporator connected to thesecond pressure reducing mechanism via a sixth tube and operationallycoupled to the compressor via at least a seventh tube. The evaporator isconfigured to receive the liquid portion from the second pressurereducing mechanism and to evaporate the liquid portion.

Other objects, features, and advantage will be apparent to persons ofordinary skill in the art from the following detailed description of theinvention and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention, needssatisfied thereby, and the objects, features, and advantages thereof,reference now is made to the following description taken in connectionwith the accompanying drawings.

FIG. 1 is a circuit diagram of a vapor compression refrigerating system,according to an embodiment of the present invention.

FIG. 2 is a Mollier chart of carbon dioxide refrigerant in the vaporcompression refrigerating system of FIG. 1.

FIG. 3 is a circuit diagram of a vapor compression refrigerating system,according to another embodiment of the present invention.

FIG. 4 is a Mollier chart of carbon dioxide refrigerant in the vaporcompression refrigerating system of FIG. 3.

FIG. 5 is an exemplary separator in which oil is separated fromrefrigerant by centrifugal separation, in which FIG. 5A is a vertical,sectional view of the separator; and FIG. 5B is a cross-sectional viewof the separator as viewed along line A-A of FIG. 5A.

FIG. 6 is an exemplary separator in which oil is separated fromrefrigerant by collision separation, in which FIG. 6A is a vertical,sectional view of the separator; and FIG. 5B is a cross-sectional viewof the separator as viewed along line A-A of FIG. 6A.

FIG. 7 is an exemplary refrigerant heat exchanging means in a vaporcompression refrigerating system, according to an embodiment of thepresent invention, in which FIG. 7A is an elevational view; FIG. 7B is aplan view thereof; and FIG. 7C is an enlarged, sectional view of a tubefor heat exchange thereof.

FIG. 8 is a perspective view of an exemplary refrigerant heat exchangingmeans in a vapor compression refrigerating system, according to anotherembodiment of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Embodiments of the present invention, and their features and advantages,may be understood by referring to FIGS. 1-8, like numerals being usedfor like corresponding parts in the various drawings.

FIG. 1 depicts a vapor compression refrigerating system according to anembodiment of the present invention. The vapor compression refrigeratingsystem may comprise a compressor 1, a radiator 2 connected to compressor1, a first pressure reducing mechanism 3 connected to radiator 2, and aseparator 4 connected to compressor 1 and to first pressure reducingmechanism 3. For example, separator 4 may comprise an oil separatorintegrated with a gas and liquid separator to form a single separator,and the radiator 2 may be a gas cooler. The vapor compressionrefrigerating system also may comprise a second pressure reducingmechanism 5 connected to separator 4, and an evaporator 6 connected tocompressor 1 and to second pressure reducing mechanism 5. Each of theconnections between the elements of the vapor compression refrigeratingsystem may be made via a tube 7.

In operation, a refrigerant, such as a carbon dioxide refrigerant, maybe compressed by compressor 1, which contracts the refrigerant andincreases the temperature of the refrigerant. The refrigerant then mayflow from compressor 1 to radiator 2, and radiator 2 may radiate therefrigerant to decrease the temperature of the refrigerant. Therefrigerant then may flow from radiator 2 to first pressure reducingmechanism 3, and first pressure reducing mechanism 3 may expand therefrigerant and may reduce the pressure of the refrigerant. Therefrigerant then may flow from first pressure reducing mechanism 3 toseparator 4, and separator 4 may separate the refrigerant into a gasportion and a liquid portion, and may separate an oil from therefrigerant. For example, the oil may be separated from the refrigerantby centrifugal separation or collision separation. The oil and the gasportion then may flow from separator 4 to compressor 1, such that theoil and the gas portion flow from separator 4 to compressor 1 via thesame tube 7. Nevertheless, the liquid portion may flow from separator 4to second pressure reducing mechanism 5, and second pressure reducingmechanism 5 may further expand and further reduce the pressure of theliquid portion. The liquid portion then may flow from second pressurereducing mechanism 5 to evaporator 6, and evaporator 6 may evaporate theliquid portion into a gas. The gas then may flow from evaporator 6 tocompressor 7.

In the above-described embodiment of the present invention, becauseseparator 4 may comprise an oil separator integrated with a gas andliquid separator to form a single separator, and/or because the gasportion of the refrigerant and the oil may flow from separator 4 tocompressor 1 via the same tube 7, the size and/or the weight of thevapor compression refrigerating system may be reduced.

FIG. 2 is a Mollier chart of carbon dioxide refrigerant in the vaporcompression refrigerating system of FIG. 1. In the Mollier chart of FIG.2, state points of the respective components are connected to each otherby lines. A curve 11 represents a saturated liquid curve and a saturatedvapor curve of carbon dioxide refrigerant, and a curve connecting bothlines is referred to as a saturation curve. A curve 12 represents anisothermal line passing through a critical point of carbon dioxiderefrigerant. Moreover, numerals labeled in FIG. 2 express the respectivecomponents depicted in FIG. 1, and they show operations of therespective components.

FIG. 3 depicts a vapor compression refrigerating system according toanother embodiment of the present invention. In this embodiment, arefrigerant heat exchanging means, e.g., a heat exchanging tube 8, isprovided for exchanging heat between the liquid refrigerant in separator4 or/and the refrigerant which flows out of separator 4, and therefrigerant which flows out of evaporator 6. In this embodiment, supercooling is possible by lowering the temperature of the refrigerantimmediately before the refrigerant flows to second pressure reducingmechanism 5. Moreover, super heating is possible for preventing liquidcompression in compressor 1, and the refrigerating ability and thereliability of the vapor compression refrigerating system may beincreased.

FIG. 4 is a Mollier chart of carbon dioxide refrigerant in the vaporcompression refrigerating system depicted in FIG. 3. In the Mollierchart depicted in FIG. 4, state points of the respective components areconnected to each other by lines. Similarly to FIG. 2, curve 11represents a saturated liquid curve and a saturated vapor curve ofcarbon dioxide refrigerant, and a curve connecting both lines isreferred to as a saturation curve. A curve 12 represents an isothermalline passing through a critical point of carbon dioxide refrigerant. Onedifference between FIGS. 2 and 4 is that there is an effect of heatexchange caused by the heat exchange between liquid refrigerant inseparator 4 and/or refrigerant which flows out of separator 4, andrefrigerant which flows out of evaporator 6. Specifically, because therefrigerant immediately before second pressure reducing mechanism 5 isthe liquid portion of the refrigerant, the liquid portion of therefrigerant moves to a position above the saturation curve. In FIG. 4,Δh2 shows a degree of super cooling, Δha shows a degree of superheating,and the effect of heat exchange due to the above-described refrigerantheat exchanging means may be expressed as about Δh1 □Δh2.

Referring to FIGS. 5A and 5B, according to an embodiment of the presentinvention, the separation of the refrigerant and the oil is performed bya centrifugal separation system. For example, the gas and liquid portionof the refrigerant may flow from first pressure reducing mechanism 3into the separator from a refrigerant flow passage 22, and therefrigerant rotates in the circumferential direction around a gasrefrigerant and oil flow passage 22 to compressor 1. Refrigerant and oilthen are separated from each other by the centrifugal force (centrifugalflow: 31). Specifically, because the pressure of the refrigerant hasbeen reduced to a pressure which is less than the critical pressure, therefrigerant and the oil are not dissolved in each other, and because thedensity of oil is greater than the density of refrigerant, the oil isstored in the lowest layer, which is an oil layer 29. Moreover, theliquid portion of the refrigerant has a greater density and is stored asa liquid refrigerant layer 28 at a position above the oil layer 29, andthe gas portion of the refrigerant is present in a gas refrigerant layer27, which is a space above the liquid refrigerant layer 28, togetherwith a small amount of liquid refrigerant at a condition of gas/liquidmixture. A refrigerant flow passage 23 to second pressure reducingmechanism 5 is positioned lower than oil layer 29, and an oil flowingout prevention plate 30 is positioned above refrigerant flow passage 23,such that a fine amount of oil existing in liquid refrigerant layer 28does not flow out together with the liquid portion of the refrigerant.The gas portion of the refrigerant in gas refrigerant layer 27 passesthrough a diffuser or tube support 26, and liquid present in the gasportion of the refrigerant is removed, such that only gas refrigerantflows into oil flow passage 24 to compressor 1. At the same time, oil issucked through an oil returning hole 25, and the sucked oil flows outtogether with the gas refrigerant. Such a structure is contained in acontainer 21.

Referring to FIGS. 6A and 6B, according to an embodiment of the presentinvention, the separation of the refrigerant and the oil is performed bya collision separation system. For example, the gas and liquid portionof the refrigerant may flow from first pressure reducing mechanism intothe separator from refrigerant flow passage 22, and the refrigerant andthe oil are separated from each other by collision with diffuser or tubesupport 26 (collision flow for separation: 32). Because diffuser or tubesupport 26 also is provided in FIGS. 5A and 5B, and refrigerant and oilare separated from each other by diffuser or tube support 26, thestructure depicted in FIGS. 5A and 5B is a structure in which thecentrifugal separation system is mainly employed and the collisionseparation system is added thereto.

FIGS. 7A-7C show an example of a structure configured to be employed inthe system of FIG. 3, in which a heat exchanging tube 41, e.g., a flattube, is provided at a storage part of liquid refrigerant of separator 4for exchanging heat between the refrigerant present in separator 4 andthe refrigerant which flows from evaporator 6. Heat exchanging tube 41may be wound at a tight contact condition at the position and itsvicinity of liquid refrigerant layer 28 of separator 4, and heatexchange may be performed. In this example, by forming heat exchangingtube 41 as a parallel multi-hole flat tube 42, the efficiency of theheat exchange may be improved. In such a structure, processing to thecontainer 21 with a pressure resistance may not be necessary.

FIG. 8 shows an example of another structure configured to be employedin the system of FIG. 3, in which a heat exchanging tube 51 having adouble-pipe structure is used for heat exchanging between the liquidportion of the refrigerant flowing into second pressure reducingmechanism 5 from separator 4 and the refrigerant which flows fromevaporator 6. In heat exchanging tube 51, in order to efficientlyperform the heat exchange between the liquid refrigerant portion flowinginto second pressure reducing mechanism 5 from separator 4 and therefrigerant which flows from evaporator 6, both flows may be set as acounter flow or a parallel flow.

The vapor compression refrigerating system according to the presentinvention may be particularly suitable for an air conditioning system ofa vehicle, such as an air conditioning system which uses carbon dioxideas a refrigerant.

While the invention has been described in connection with embodiments ofthe invention, it will be understood by those skilled in the art thatvariations and modifications of the embodiments described above may bemade without departing from the scope of the invention. Otherembodiments will be apparent to those skilled in the art from aconsideration of the specification or from a practice of the inventiondisclosed herein. It is intended that the specification and thedescribed examples are consider exemplary only, with the true scope ofthe invention indicated by the following claims.

1. A vapor compression refrigerating system comprising: a compressorconfigured to compress a refrigerant; a radiator connected to thecompressor via a first tube, wherein the radiator is configured toreceive the refrigerant from the compressor and to radiate therefrigerant; a first pressure reducing mechanism connected to theradiator via a second tube, wherein the first pressure reducingmechanism is configured to receive the refrigerant from the radiator andto reduce a pressure of the refrigerant; a separator connected to thefirst pressure reducing mechanism via a third tube and the compressorvia a fourth tube, wherein the separator is configured to receive therefrigerant from the first pressure reducing mechanism, and theseparator comprises: an oil separator which is configured to separate anoil from the refrigerant; and a liquid and gas separator formed integralwith the oil separator, wherein the liquid and gas separator isconfigured to separate a liquid portion and a gas portion from therefrigerant, and the separator is further configured to transmit the oiland the gas portion to the compressor via the fourth tube; a secondpressure reducing mechanism connected to the separator via a fifth tube,wherein the second pressure reducing mechanism is configured to receivethe liquid portion from the separator and to reduce a pressure of theliquid portion; and an evaporator connected to the second pressurereducing mechanism via a sixth tube and operationally coupled to thecompressor via at least a seventh tube, wherein the evaporator isconfigured to receive the liquid portion from the second pressurereducing mechanism and to evaporate the liquid portion.
 2. The vaporcompression refrigerating system of claim 1, wherein the evaporator isconnected to the compressor via the separator, and the evaporator isconfigured to receive the liquid portion from the second pressurereducing mechanism and to evaporate the liquid portion into anevaporated portion and to transmit the evaporated portion to theseparator, wherein the system further comprises means for exchangingheat between the liquid portion and evaporated portion.
 3. The vaporcompression refrigerating system of claim 1, wherein the oil separatorcomprises at least one of a centrifugal oil separator and a collisionoil separator.
 4. The vapor compression refrigerating system of claim 1,wherein the first pressure reducing mechanism is configured to control apressure of the refrigerant at an exit side of the first pressurereducing mechanism to be less than or equal to a critical pressure. 5.The vapor compression refrigerating system of claim 1, wherein at leastone of the first pressure reducing mechanism and the second pressurereducing mechanism comprises a mechanical expansion valve which changesa degree of expansion in response to at least one of a temperature and apressure of the refrigerant.
 6. The vapor compression refrigeratingsystem of claim 1, wherein at least one of the first pressure reducingmechanism and the second pressure reducing mechanism comprises anelectronic expansion valve which changes an opening degree of a valve byan electric signal in response to at least one of a temperature and apressure of the refrigerant.
 7. The vapor compression refrigeratingsystem of claim 1, wherein the refrigerant comprises carbon dioxide. 8.An air conditioning system comprising a vapor compression refrigeratingsystem, wherein the vapor compression refrigerating system comprises: acompressor configured to compress a refrigerant; a radiator connected tothe compressor via a first tube, wherein the radiator is configured toreceive the refrigerant from the compressor and to radiate therefrigerant; a first pressure reducing mechanism connected to theradiator via a second tube, wherein the first pressure reducingmechanism is configured to receive the refrigerant from the radiator andto reduce a pressure of the refrigerant; a separator connected to thefirst pressure reducing mechanism via a third tube and the compressorvia a fourth tube, wherein the separator is configured to receive therefrigerant from the first pressure reducing mechanism, and theseparator comprises: an oil separator which is configured to separate anoil from the refrigerant; and a liquid and gas separator formed integralwith the oil separator, wherein the liquid and gas separator isconfigured to separate a liquid portion and a gas portion from therefrigerant, and the separator is further configured to transmit the oiland the gas portion to the compressor via the fourth tube; a secondpressure reducing mechanism connected to the separator via a fifth tube,wherein the second pressure reducing mechanism is configured to receivethe liquid portion from the separator and to reduce a pressure of theliquid portion; and an evaporator connected to the second pressurereducing mechanism via a sixth tube and operationally coupled to thecompressor via at least a seventh tube, wherein the evaporator isconfigured to receive the liquid portion from the second pressurereducing mechanism and to evaporate the liquid portion.
 9. A vehiclecomprising an air conditioning system, wherein the air conditioningsystem comprises a vapor compression refrigerating system, and the vaporcompression refrigerating system comprises: a compressor configured tocompress a refrigerant; a radiator connected to the compressor via afirst tube, wherein the radiator is configured to receive therefrigerant from the compressor and to radiate the refrigerant; a firstpressure reducing mechanism connected to the radiator via a second tube,wherein the first pressure reducing mechanism is configured to receivethe refrigerant from the radiator and to reduce a pressure of therefrigerant; a separator connected to the first pressure reducingmechanism via a third tube and the compressor via a fourth tube, whereinthe separator is configured to receive the refrigerant from the firstpressure reducing mechanism, and the separator comprises: an oilseparator which is configured to separate an oil from the refrigerant;and a liquid and gas separator formed integral with the oil separator,wherein the liquid and gas separator is configured to separate a liquidportion and a gas portion from the refrigerant, and the separator islurer configured to transmit the oil and the gas portion to thecompressor via the fourth tube; a second pressure reducing mechanismconnected to the separator via a fifth tube, wherein the second pressurereducing mechanism is configured to receive the liquid portion from theseparator and to reduce a pressure of the liquid portion; and anevaporator connected to the second pressure reducing mechanism via asixth tube and operationally coupled to the compressor via at least aseventh tube, wherein the evaporator is configured to receive the liquidportion from the second pressure reducing mechanism and to evaporate theliquid portion.